fix typo in class 'Interface' (#1135)

Author: JMmmmuu

graphene/types/interface.py

@@ -68,4 +68,4 @@ def resolve_type(cls, instance, info):
             return type(instance)
 
     def __init__(self, *args, **kwargs):
-        raise Exception("An Interface cannot be intitialized")
+        raise Exception("An Interface cannot be initialized")